Hinged braces for placing against a door to prevent the door being opened are well known, but none of the known braces has a satisfactory self-locking hinge which secures the brace in position against the door.
The patent to Notthoff, U.S. Pat. No. 790,653, shows a device which engages under the handle of a closed door when the hinge is straightened, but the hinge is not self-locking. The door brace of Notthoff requires a removable hinge pin to release the hinge. The patent to Gayman, U.S. Pat. No. 4,231,599 shows a door brace having a complicated foot device and a chain device to secure the safety brace to the door. The door guard of Spurr, U.S. Pat. No. 4,139,227 has adjustable pivotable members which are overlapped, forming a weak point where the upper member engages against the lower member. Lane, U.S. Pat. No. 4,300,796, also shows an adjustable prop which has an inner member extending from within an outer member without provision of a hinge. The patent to Peters, U.S. Pat. No. 4,157,128, shows a ladder hinge which has a complex self-locking feature including a pair of circular plates rigidly fixed to opposite faces of one ladder member and rotatably connected to the other ladder member, the hinge being locked by means of a locking ring slidably engaged with the other member. The door brace of Jost, U.S. Pat. No. 4,036,518, also has one member extending from within the other member to the required length, without using a hinge.